Abstract
Purpose
To investigate the effect of xenon (Xe) and nitrous oxide (N2O) on norepinephrinergic neuronal activity in the rat medial preoptic area (mPOA) and posterior hypothalamus (PH) using microdialysis.
Methods
Sixty male Wistar rats were equally allocated to two groups: mPOA and PH. A microdialysis probe was implanted into the mPOA or the PH. In both groups, each animal was exposed to one of the following inhalations: 25% oxygen (control,n = 6), 30% Xe (n = 6), 60% Xe (n = 6), 30% N2O (n = 6) or 60% N2O (n = 6). Norepinephrine concentration in the perfused artificial cerebrospinal fluid was measured by high pressure liquid chromatography at ten-minute intervals. After plotting the time-norepinephrine concentration curve, the area underthe curve (AUC) in each group was calculated.
Results
In the mPOA, 30 and 60% Xe, but only 60% N2O significantly increased norepinephrine release. The AUC in the 30% Xe, 60% Xe or 60% N2O group was 160 ± 9 (P < 0.05), 288 ± 42 (P < 0.01) or 237 ± 46 pg·min/sample (P < 0.01), respectively, compared to that in the control group: 77 ± 14 pg·min/sample. In the PH, only 60% Xe significantly increased norepinephrine release compared to control (AUC: 191 ± 38vs 71 ± 1 pg·min/sample,P < 0.01).
Conclusion
The present data suggest that Xe stimulates norepinephrinergic neurons more potently than N2O; 1.2 times more in the mPOA and 2.5 times more in the PH. This stimulant effect may contribute to the hypnotic and sympathotonic effects of Xe in rats.
Résumé
Objectif
Rechercher, à l’aide de la microdialyse, l’effet du xénon (Xe) et du protoxyde d’azote (N2O) sur l’activité neuronale de la noradrénaline dans l’aire préoptique médiane (APOm) et dans l’hypothalamus postérieur (HP) de rats.
Méthode
Soixante rats mâles Wistar ont été répartis également en deux groupes: APOm et HP. Une sonde à microdialyse a été implantée dans l’APOm et l’HP Chaque animal a été exposé à l’une des inhalations suivantes: 25% d’oxygène (témoin, n = 6), 30% de Xe (n = 6), 60% de Xe (n = 6), 30% de N2O (n = 6) ou 60% de N2O (n = 6). La concentration de noradrénaline du liquide céphalorachidien artificiel perfusé a été mesurée par Chromatographie liquide haute performance à des intervalles de dix minutes. Après avoir tracé la courbe de la concentration de noradrénaline en fonction du temps, on a calculé l’aire sous la courbe (ASC) pour chaque groupe.
Résultats
Dans l’APOm, les concentrations de 30 et 60% de Xe, et de 60% seulement de N2O, ont augmenté significativement la libération de noradrénaline. Les ASC dans les groupes à 30% de Xe, 60% de Xe ou 60% de N2O a été de 160 ± 9 (P< 0,05), 288 ± 42 (P < 0,01) ou 231 ± 46 pg·min/échantillon (P < 0,01), respectivement, comparés à celle du groupe témoin: 77 ± 14 pg·min/échantillon. Dans l’HP seul le Xe à 60% a augmenté sensiblement la noradrénaline comparé au groupe témoin (ASC: 191 ± 38 vs 71 ± 1 pg·min/échantillon, P < 0,01).
Conclusion
Les présentes données suggèrent que le Xe stimule les neurones noradrénalinergiques de façon plus importante que le N2O, soit 1,2 fois plus dans l’APOm et 2,5 fois plus dans l’HP Cet effet stimulant peut contribuer aux effets hypnotique et sympathicotonique du Xe chez les rats.
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Supported in part by Grant-in-aid for scientific research (No 09470323) from the Minister of Education, Science and Culture in Japan.
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Yoshida, H., Kushikata, T., Kubota, T. et al. Xenon inhalation increases norepinephrine release from the anterior and posterior hypothalamus in rats. Can J Anesth 48, 651–655 (2001). https://doi.org/10.1007/BF03016198
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DOI: https://doi.org/10.1007/BF03016198